Method for making Arundo donax paper product

ABSTRACT

Composite panels and pulp, and paper products of the pulp, are produced from  Arundo donax.  In the fabrication of the composite panels,  Arundo donax  is comminuted to a suitable size, combined with a binder, and consolidated into panels that meet standards for construction and/or furniture grade panels. The  Arundo donax  particulates may be combined with wood particulates to produce a mixed furnish that can be used in the preparation of composite panels. Comminuted  Arundo donax  is treated, in conventional pulping processes, to produce a high tensile strength pulp that can be used in the production of paper. The pulp has a lighter color than wood pulp, and thereby uses less bleaching chemicals to achieve a desired whiteness. The pulp can be combined with wood pulp to produce a variety of products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending internationalapplication number PCT/US99/13519, filed Jun. 16, 1999, which claims thebenefit of the priority of the filing date of U.S. patent applicationNo. 60/089,596, filed Jun. 17, 1998. The benefit of the priority of thefiling dates of each is hereby claimed under 35 U.S.C. §§ 120 and 119,respectively. Each of the above-identified applications is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The invention pertains to composite panels and engineered products madeof Arundo donax (a type of grass), and pulp and paper produced fromArundo donax.

BACKGROUND OF THE INVENTION

There are several well-known technologies for producing particle board,using wood chips and other wood processing waste products. Indeed, thesewood-based composite boards have found wide application particularly inbuilding construction and the manufacture of furniture. More recently,the industry has produced oriented strand board (OSB) as a usefulconstruction material. Both particle board and OSB fall into thecategory of “composites” because both contain a filler (wood fiber)embedded within a binder matrix. Another well-known wood composite is“MDF” (medium density fiber board). Other well known composite productsare made with wood or other fibers using inorganic binders, such ascement, to make construction and decorative products.

The popularity of wood-based composites is based in large part on theavailability of relatively low cost wood byproducts (chips, sawdust,etc.) that can be used in the composites. Indeed, many of the industrystandards for the physical performance of these composites are based onwood-based composites. Since the manufacturing parameters for wood-basedcomposites are well-known, and can often be customized for certainapplications, there has been little incentive to investigate otherfillers.

With the increasing demand for paper prepared from wood pulp, as well asworldwide demand for wood-based composites (which can substitute forlumber), there is now a perceived growing need for a substitute rawmaterial for wood. While the supply of wood for use in these products is“renewable,” it requires setting aside land for long periods of time fortree farming. Moreover, when demand outstrips supply, because supply isbased on forecasts of decades before when trees were planted, then ashortage inevitably develops. Since the wood required for these usesresults in cutting millions of acres of forest each year, such shortageslead to serious worldwide concerns about large scale deforestation andits contribution to global warming.

There is yet a need for a material that can be readily substituted forwood in wood-based composites, and that can also be used to producepaper pulp for the fabrication of paper products. Extensive research hadbeen conducted and production trials have been made in an effort to finda suitable non-wood fiber for composites and pulp but, until now, thiswork has met with very little success due to inferior properties,excessive costs and many commercial production drawbacks.

SUMMARY OF THE INVENTION

In one aspect of the invention, Arundo donax particles are provided. Theparticles, including chips and flakes, can be advantageously formed intopulp from which paper and paper products can be made. The particles canalso be used in the production of particle boards.

In another aspect, the invention provides composites that include abinder matrix filled with Arundo donax particulates. In accordance withthe invention, these composite boards use significantly less binder thanwood-based composites, and exceed several of the physical properties ofcomparable wood-based composites, as measured by standards used in theindustry.

The composites of the invention are produced by selecting nalgrass (acommon name for Arundo donax), which is widely distributed as a nativewild grass in many parts of the world. The nalgrass is charged to aflaker which contains sharp internal knife edges to reduce the nalgrassto small shards (e.g., flakes), which can then be charged to ahammermill for further size reduction. The resulting material is calleda “furnish.” The hammermill furnish is sized, preferably into at leasttwo fractions. Each of the two fractions of nalgrass particulates isseparately combined with a proportion of a resin. A layered structure,having alternate layers of fine and coarse nalgrass-resin mixture isthen produced. The layered structure is subjected to heat and pressurefor consolidation into a composite product. Satisfactory products may bemade with a single layer, two layers, or more. Many commercialoperations blend a variety of wood sources, such as hardwoods,softwoods, and recycled wood waste, in the manufacture of composites.Those skilled in the field will seek the advantages of nalgrass byblending into their furnish a portion of nalgrass with their availablewood sources.

The invention also provides paper pulp, and paper products made fromnalgrass. The raw pulp produced from the nalgrass is of lighter colorthan the pulp produced from woods that are typically used in paperproduction. Accordingly, a smaller amount of chemical bleach must beadded to bleach the pulp to a desired whiteness. Nalgrass pulp is alsostronger than most common hardwoods, such as aspen. The pulp of thepresent invention can also be utilized in other cellulose-based productsincluding building products and modified cellulosic fibers such asviscose (e.g., rayon).

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an illustration of representative nalgrass particles of theinvention;

FIG. 2 is a plan view of a representative device for forming nalgrasschips in accordance with the present invention;

FIG. 3 is an elevation view of a representative device for formingnalgrass chips in accordance with the present invention;

FIG. 4 is a detail section of a blade arrangement for a representativedevice for forming nalgrass chips in accordance with the presentinvention;

FIG. 5 is a schematic flow diagram showing steps in a representativeprocess for producing the nalgrass composites of the invention;

FIG. 6 is a representative nalgrass composite panel prepared inaccordance with the invention;

FIG. 7 is an illustration comparing production from kenaf, hardwood, andArundo donax harvests; and

FIG. 8 is a schematic flow diagram showing steps in representativeprocesses for producing nalgrass pulp in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The composites of the invention utilize a raw material that is abundant,but that has been regarded as a weed, unsuitable for any use other thanstabilizing soil on slopes, windbreaks, and the manufacture of woodwindinstruments. The raw material is of the genus Arundo of the familyGramineae, tribe Festuccae. It includes about six species, of whichArundo donax L. is the most widely distributed and the best known.Arundo donax, also known as “nalgrass,” is native to the countriessurrounding the Mediterranean Sea. The terms “nalgrass” and “Arundodonax” are used interchangeably herein.

Nalgrass is a tall, erect, perennial grass and at maturity reaches 7-28feet in height. In optimum climate, it grows at a rate of six inches perday during most of the year and can reach maturity in one to one and ahalf years. In infertile soils, yields are in the range of 8 tons drynalgrass material per acre. Test cutting in southern California resultedin yields of more than 30 tons dry nalgrass material per acre. It isestimated that the sustainable yield of dry fiber from 50,000 acres ofnalgrass is the equivalent of 1,250,000 acres of tree wood fiber. It isone of the largest of the herbaceous grasses. Unlike bamboo, kenaf, andother grasses, the stalks are hollow, with walls 2 to 7 mm. thick anddivided by partitions at the nodes. The nodes vary in length fromapproximately 12 to 30 cm. The outer tissue of the stem is of asiliceous nature, very hard and brittle with a smooth, glossy surfacethat turns pale golden yellow when fully mature.

The vascular bundles of nalgrass are distributed freely throughout thecross-sectional area of its fundamental parenchyma. Those toward theperiphery of the stem are smaller and more numerous than those towardthe interior. These bundles are collateral and are surrounded by one ormore rows of thick-walled, strongly lignified fibers. Toward theperiphery of the stem, as the size of the bundles decreases, the numberof rows of fibers associated with the bundles are small andcomparatively close together, the fibers are sufficiently abundant toform a continuous ring of structural tissue within which are scatteredthe vascular elements. This structural ring is separated from awax-covered single cell epidermal layer by a narrow band of parenchymacells that in mature stems are comparatively small, thick-walled, andlignified. The vascular bundles, including the associated fibersinterior to the structural fibrous ring, occupy approximately 24% of thestem. The vascular tissue and associated fibers that compose thestructural ring make up approximately 33% of the total cross-sectionalarea. Thus, parenchymatous tissue occupies but 43% of thecross-sectional area of the stem.

Both leaves and stems of nalgrass, particularly the former, containnumerous highly silicified cells. These cells, associated with thevascular bundles, are also located in the epidermal tissue. Theirpresence explains the elevated silica count that has been indicated bychemical analyses.

The equipment necessary for manufacturing the composites of theinvention are commercially available, and may have to be modified tooptimize production. Nevertheless, commercially available equipment canreadily be used in the process.

In one aspect the present invention provides an Arundo donax particle.The particle is either a chip or a flake and can be used either in theformation of pulp, paper products derived from the pulp, or incorporatedinto composite panels.

The chip is formed from an Arundo donax stem by cutting the stem acrossits length to provide a ring having a substantially circular crosssection in a length from about ⅛ inch to about 3 inches. Breaking thering's circular cross section provides the chip. Typically, when thering is broken two to five chips are formed. Referring to FIG. 1, Arundodonax's stem 1 provides ring 2 from which chips 3 are formed. Arepresentative device and method for forming Arundo donax's chips isdescribed in Example 1. Preferably, the ring has a length from about ½to about 1½ inches and is formed by cutting the stem either by a sawcut, a knife blade or a veneer cut.

In addition to chips, suitable Arundo donax particles include flakes.The flakes are formed from flaking an Arundo donax stem in any one of anumber of conventional flakers. Preferably, the flake (i.e., shard,sliver) has a length from about two inches to about four inches andpreferably from about 2½ to about 3½ inches. Flake thickness can varygreatly from about {fraction (1/32)} of an inch to about ⅛ of an inch.Referring to FIG. 1, flaking stem 1 provides flake 4. Suitable flakescan be prepared from conventional equipment including ring, drum, anddisc flakers and chippers. Preferably, flakes are formed using a drumflaker.

As discussed below, Arundo donax particles (e.g., flakes and chips) canbe advantageously used in the production of composite panels, pulp, andpaper products. Chips can be advantageously used in the formation ofpulp including continuous or batch pulping processes. Arundo donaxflakes can also be pulped, preferably by batch digestion processes. Inkraft pulping the flakes and/or chips are directly digested. In CTMP(alkaline peroxide) pulping, the flakes and/or chips can be reduced insize prior to digestion. For composite panel (e.g., particle board)formation, the flakes and/or chips are typically reduced in size byhammermilling to provide a furnish which is then mixed with a bindersuch as a resinous binder and then consolidated into a panel.

A representative method for forming a composite panel is illustrated inFIG. 5. Referring to FIG. 5, in a first step clean nalgrass is chargedto a flaker or chipper 10 which contains internal sharp edges forcutting the nalgrass to a reduced size. Typically, a size distributionof nalgrass is obtained from the flaker. Preferably, nalgrassparticulates having a length of about one inch, and up to about fourinches, are produced by the flaker, if the resultant furnish is to beused to manufacture composites. If the particulates are to be used tomanufacture paper pulp, then it is preferred that they be smaller,typically in the range one-half inch to about 1½ inches in length.

The nalgrass particulates are then charged to a hammermill 20 forfurther comminution. It should be understood that other apparatuscommonly used for comminution of cellulosic materials may also be used,and that the invention is not limited to the use of flakers, chippers,and hammermills. The hammermill further reduces the size of the nalgrassparticulates and produces a size distribution of the furnish.

The particulates from the hammermill are then preferably charged to aseries of mesh sieves 30 for sizing. Preferably, the sieves are arrangedto produce at least three cuts or size distributions of nalgrassparticulates. Thus, it is preferred to use a first sieve of 48 mesh sizeto remove undersized nalgrass “dust.” Thereafter, the oversizedparticulates are charged to a second sieve of mesh size 14. This sieveproduces an undersize and an oversize. Material that does not passthrough a 4 mesh (over one-quarter inch) is removed and reworked.

The undersized material is finer and is used to make the “face” layers100 of the composites shown in FIG. 6. The oversize material, which isrelatively coarser, is used for the core layer 120 or layers of thecomposite. Typically, a composite comprises three layers: a central corecovered on each side by a face layer. However, additional layers canalso be added, depending upon customer requirements, physical propertyrequirements, and other factors.

The undersize or “face nalgrass particulates” are mixed with a resin 40to form a “face material mixture” of resin-coated particulates.Separately, the core material is also mixed with the resin to form a“core material mixture.”

While any of the organic resins and inorganic binders conventionallyused in the manufacture of wood products may also be used to makenalgrass composites, the preferred resin is methyl diisocyanate (“MDI”).It has been found that MDI resin results in the production of compositeshaving superior properties. Without being bound, it is theorized thatthe nalgrass-MDI resin combination may produce these enhanced physicalproperties due to a combination of any of the listed physical propertiesof nalgrass in combination with moieties of the MDI resin molecule: highmelting point waxes present in the nalgrass, elevated silica content ofthe nalgrass, high-alpha cellulose content of the nalgrass, and lowlignin content of the nalgrass.

Regardless of theory, it has also been found that the manufacture ofnalgrass composites requires a lower proportion of resin additive, thanwould be required with a wood-based composite of a similar physicaldimensions and strength. Indeed, nalgrass composites of the inventionmay be prepared with as little as 1.5 weight percent MDI. Typically, theresin proportion may range from about 1.5 to about 5 weight percent MDIdepending upon the composite physical properties required. More than 5weight percent MDI may also be used but there appears to be of littlecommercial advantage to produce such composites. Generally, the higherthe proportion of resin added, the stronger the composite. Preferably,the nalgrass-resin mixture contains from about 1.5 to about 3.5 weightpercent MDI, and most preferably from about 2.5 to about 3.0 weightpercent MDI. Clearly, when a resin other than MDI is used, a differentresin proportion may be found optimal, depending upon the physicalproperties required of the composite.

After the nalgrass-resin mixtures have been prepared, they are conveyedto “mat forming” 60. In this process, the face material mixture is firstlaid down in a layer. This is followed by a layer of core materialmixture, which is covered by a final layer of face mixture, to form athree-layer sandwich. More or less layers can also be used dependingupon the desired properties of the resultant composite.

The layered mat is prepressed 70 under ambient conditions to reduce itsvolume, by allowing limited movement of particulates to fill ininterstitial and void spaces. The prepressed layered structure is thenpressed, in a conventional press used for the production of wood-basedcomposites, and subjected to sufficient heat and pressure to consolidatethe panel 80. When MDI resin is used, the press is typically operated ata temperature in the range of 160-170° C. (320-340° F.), and underpressure of between 500-600 psi (maximum) during the closing cycle andabout 100 psi during the curing cycle.

During pressing, some of the mixture may spread outward, resulting in arelatively uneven edge to the consolidated composite. The panel edgesare trimmed, and the board is cut to size to produce a composite boardof standard size. The formation of representative nalgrass particleboards and their properties as well as wheatstraw-based particle boardsand southern pine-based particle boards is described in Example 2.

As noted above, the nalgrass furnish may be mixed with proportions ofwood furnish to prepare composites in accordance with the invention.Preferably, the nalgrass forms the major proportion of the furnish dueto its lower cost. The formation of representative nalgrass/southernpine particle boards and their properties are described in Example 3.The mechanical and physical properties of the nalgrass/southern pineblend particle boards are compared to particle boards formed from (1)nalgrass and (2) southern pine in that example.

The Arundo donax composite panel includes a binder matrix and Arundodonax particles (e.g., chips, flakes, and chips and flakes havingreduced size) distributed throughout the binder matrix. Referring toTables 1 and 2, the composite panels of the present invention meet atleast the M-3 standard for composite panels.

The panels include from about 1% to about 10% by weight of a resinbinder based on the total weight of the panel. However, to achieve theadvantageous properties associated with wood panels, the presence ofArundo donax in the composite panels of the present invention permits amuch lower amount of binder. Accordingly, the panels preferably includefrom about 1.5% to about 3.0% by weight of resin binder based on thetotal weight of the panel. Conventional binders known in the formationof composite panels can be used to provide the panels of the invention.Preferred binders include methyl diisocyanate, urea-formaldehyde, andphenolic binders.

The panels of the present invention can further include other fibersincluding wood fibers. Preferably, the panels of the invention thatinclude a blend of fibers have from about 10% to about 90% by weightArundo donax particles based on the total weight of the panel.

Generally, the bending strength and moisture resistance of the panels ofthe invention are increased proportionally relative to the amount ofArundo donax present in the panel compared to conventional wood-basedpanels. Generally, the bending strength of the panel is about 55%greater than a similar constituted wood-based panel, and about 5%greater than a similarly constituted wheatstraw-based panel. Themoisture resistance of the panel is about 2.6 times greater than asimilarly constituted wood-based panel and about 15% greater than asimilarly constituted wheatstraw-based panel.

A representative method for manufacturing an Arundo donax compositepanel includes the steps of (1) comminuting Arundo donax into particlesof a size distribution suitable for use as a furnish in a compositepanel; (2) mixing those particles with a binder (e.g., resin) to providea binder-particle mixture; and (3) consolidating the binder-particlemixture into a composite panel. In the process, the Arundo donaxparticles are bonded into a contiguous material with the resin. As notedabove, the particle-binder mixture can further include other materialssuch as, for example, wood particles and fibers.

As described above, Arundo donax can be advantageously incorporated intoparticle board. Similar advantages can be obtained through theincorporation of Arundo donax in oriented strand board (OSB) and mediumdensity fiberboard (MDF). Arundo donax can be incorporated as the soleparticular component or as a component in a particle blend.

In another aspect of the invention, nalgrass is utilized as a rawmaterial for the preparation of pulp and paper products produced fromthis pulp. Arundo donax pulp comprises fibers obtained from thetreatment of Arundo donax particles (e.g., chips and flakes). Dependingupon the pulp, in addition to treatment, the particles can also besubject to comminution. Comminution can be performed by a number ofdevices including, for example, a hammermill or a rotary disc refiner.

As discussed below, the pulp can be formed from a number of differenttreatments including, for example, kraft pulping, soda pulping, alkalineperoxide mechanical pulping (CTMP), sulfite, and other pulping processesknown in the art. The pulping process can also include bleaching. In apreferred process, the bleaching step includes Elemental Chlorine-Freebleaching.

The Arundo donax pulp of the present invention has a freeness in a rangefrom about 150-750 CSF and has a brightness of at least about 55% ISO,and preferably at least about 75% ISO.

The pulp forming methods of the invention provide a pulp yield of about50%. The yield is comparable to that of hardwood yields andsignificantly greater than that obtained from kenaf. The yields obtainedfrom Arundo donax, hardwood, and kenaf are illustrated in FIG. 7.Referring to FIG. 7, the initial yields of usable kenaf, hardwood, andArundo donax are about 50 pounds/100 pounds, about 88 pounds/100 pounds,and about 99 pounds/100 pounds, respectively. For kenaf, separation ofthe pith greatly reduces the usable amount of fiber. For hardwood,debarking provides a relatively high amount of fiber for furtherprocessing. Arundo donax initial processing removes only the leaves fromthe stem, which are unusable, leaving the majority of the Arundo donax(i.e., about 99%) usable for further processing. Following initialprocessing, the kenaf, hardwood and Arundo fibers are then digested witha typical yield being about 50%. As illustrated in FIG. 7, the power(steam requirement, BTU/ton) and chemical requirements (lbs/ton) forpulping Arundo donax is significantly less than for pulping of eitherkenaf or hardwood fibers. The power requirement for Arundo donax pulpingis approximately 88% that of kenaf and about 73% of hardwood digestion.Furthermore, Arundo donax pulping requires about 83% of the amount ofthe chemicals needed to convert the raw fibers to usable pulp. Theoverall pulp yields for kenaf, hardwood, and Arundo donax are about 28%,44%, and 50%, respectively. Thus, the use of Arundo donax in theformation of pulp and subsequent paper products, offers significanteconomic advantages through lower energy and chemical requirementscompared to hardwood and other non-wood materials. As illustrated in theexamples, the characteristics of Arundo donax pulp, paper products, andparticle boards is generally comparable or superior to wood-based andnonwood-based counterparts.

The pulp has a better tear and tensile strength than aspen pulp. This isan important property affecting paper production efficiency. Also, thenalgrass furnish uses less chemicals and energy to produce pulp.

The bulk density of nalgrass chips is somewhat higher than that oftypical wood chips. Accordingly, digester loading would beproportionately higher for nalgrass chips than for wood chips. This isan important consideration for those paper and pulp manufacturers thatare limited in capacity due to digester through-put limitations.

In contrast to wood chips, which require a moisture content of about 50percent for efficient pulping, nalgrass particles having significantlylower moisture content, less than about 10 percent, can be directly andreadily digested.

The nalgrass chips or particulates are readily susceptible to digestion,and cook very readily as compared to wood under kraft conditions forwood. The yield of unbleached pulp is of the order of 48.5%, which atthe upper end of the range for bleachable kraft pulps, with the possibleexception of aspen (which produces yields in the range 55 to 58%).Importantly, the pulp of nalgrass has a lighter color than typicallyobtained from hardwood. Accordingly, a lower amount of bleachingchemicals is added to produce the same resultant treated brightness. Thebrown stock produced from nalgrass is very easily bleached with a DEDEDsequence to 89.9% ISO brightness at a 93.9% yield. The brown stock canalso be readily bleached by the Elemental Chlorine Free (ECF) method, athree-stage method, as described in Example 4 and FIG. 8. In arepresentative ECF process, pulp brightness of about 85% ISO wasobtained.

The weighted average fiber length of nalgrass pulp is about 0.97millimeter, and the coarseness is of the order of 0.13 milligram permeter. Both of these values are somewhat higher than obtained from aspenpulp.

Nalgrass pulp may be used to prepare paper, such as wood-free uncoatedpapers, and may also be blended with wood pulps to produce otherproducts. Nalgrass wood pulp is also suitable for the production ofcorrugating medium. Nalgrass furnish may be blended with wood furnish toproduce a mixed pulp product suitable for many uses.

In another aspect of the present invention, methods for forming Arundodonax pulp are provided. In these methods, Arundo donax particles suchas chips and flakes are pulped.

In one method, Arundo donax pulp is formed by selecting a furnish thatincludes Arundo donax particles and subjecting the furnish to a pulpingprocess to produce a brown stock of pulp having a yield of about 48% byweight based on the furnish. Generally, the pulping time for the method,which achieves a 48% yield and a kappa value of about 15, is about 25%less than required for pulping hardwood to achieve the same yield andkappa value.

In another embodiment, the present invention provides a method forforming an Arundo donax pulp that includes the steps of: (1) selecting afurnish that includes Arundo donax particles; (2) subjecting the furnishto a pulping process to produce a brown stock of pulp having a yield ofabout 48% by weight based on the furnish; and (3) bleaching the brownstock to a brightness of from about 55% to about 90% ISO. In the method,bleaching the brown stock to a brightness of about 90% ISO requiresabout 25% less bleach than required for bleaching hardwood to about thesame brightness.

In another embodiment of the method of the invention, Arundo donax pulpis formed by: (1) subjecting Arundo donax particles to a bleachingchemical to provide a bleached furnish; and (2) mechanically refiningthe bleach pulp furnish to provide a pulp stock having a brightness offrom about 55% to 90% ISO. The bleaching chemicals can be any one of avariety of bleaching chemicals known to those in the pulping art.Preferred bleaching chemicals include a mixture of hydrogen peroxide,sodium hydroxide, and sodium silicate (alkaline peroxide pulping).Alternatively, the bleaching chemical can include chlorine dioxide.

A flow chart illustrating two representative pulping processes is shownin FIG. 8. Referring to FIG. 8, kraft pulping and bleaching andchemimechanical pulping (alkaline peroxide) processes are illustrated.Briefly, in these processes nalgrass stems are processed to formnalgrass particles (e.g., chips and/or flakes). For kraft pulping andbleaching, the nalgrass particles are digested in a cooking liquor. Thedigested material is then washed and the waste liquor recycled into thecooking liquor for continuous processing. The result of digestion is apulp product that is then bleached. As illustrated in FIG. 8, bleachingcan include the steps of a first chlorine dioxide bleaching stepfollowed by an extraction step which is then followed by a secondchlorine dioxide bleaching step. Following bleaching, the pulp is thenwashed and either directed to a paper machine for paper formation orpressed and dried for shipping to market. The pressed and dried pulp isreferred to as market pulp.

For chemimechanical pulping, the nalgrass particles are impregnated withchemical (an alkaline peroxide mixture of hydrogen peroxide, sodiumhydroxide, and sodium silicate). Following chemical impregnation, theresulting treated pulp is mechanically refined and then washed. Afterwashing the pulp can either be directed to a paper machine or dried andbaled and shipped to market.

In another aspect of the present invention, Arundo donax paper productsare provided. The paper products include Arundo donax pulp. Theincorporation of Arundo donax pulp into the paper products providesadvantageous brightness as well as strength (i.e., burst, tear, andtensile). The utilizing of Arundo donax in the production of paper, itspulping behavior and pulping properties are described in Example 4. InExample 4, data from kraft pulping, soda pulping, and alkaline peroxidemechanical pulping is presented. The results for Arundo donax arecompared to those obtained for wheatstraw and wood.

The Arundo donax paper products are generally formed by a method thatincludes the steps of: (1) forming an Arundo donax furnish that includesfibers and an aqueous dispersion medium (e.g., water); (2) depositingthe furnish onto a foraminous support (e.g., a forming wire); (3)dewatering the deposited furnish to provide a fibrous web; and (4)drying the web to provide a paper product.

The Arundo donax paper products of the present invention can furtherinclude other materials and can include a pulp blend, such as a blend ofArundo donax and softwood and/or hardwood pulp. Accordingly, in themethod described above, the Arundo donax furnish can further includewood fibers.

The advantageous properties of Arundo donax can be obtained byincorporating from about 5% to about 85% by weight Arundo donax pulp inthe paper product. Generally, the paper product of the present inventionhas a brightness of at least about 82% ISO, a burst index of at leastabout 3.0, a tear index of at least about 8.5, and a tensile index of atleast about 50. Depending upon the characteristics of the pulp, thepaper products of the present invention include high brightness printingand writing grade paper, news print and publication printing grade, andunbleached liner and corrugation boards.

The following examples are provided for the purposes of illustration andnot limitation.

EXAMPLES Example 1

Equipment Processes, and Methods for Nalgrass Size Reduction

In this example, cutting or macerating nalgrass, more specificallycutting nalgrass into particles that are suitable for processing intodigested pulp or for efficient processing into composite panels and/orengineered wood products, is described.

Fairly sophisticated processing equipment has been developed over manyyears, by the forest and wood products industries, for size reduction oflogs, sawmill shavings, waste lumber, etc. The equipment and handlingmethods have been designed to produce particles of specific geometry foruse in modern digesters for the manufacture of pulp and in millingequipment for wood composites, namely, particleboard, oriented strandboard (OSB), and medium density fiberboard (MDF). During the developmentwork, several types and models of wood chippers and flakers were tested.The resulting particles were satisfactory for laboratory and pilot scalework but it quickly became evident that such particle geometry was lesssatisfactory for commercial application.

Generally, the conventional equipment, ring, drum, and disc flakers andchippers, and various tub and agricultural and “roadside/yard” grinders,produced many long flakes, shards, and slivers. The action of thesemachines tend to pull the hollow nalgrass stems into the blades andshred the long fibers as if peeling layers. Long shards and slivers tendto blind screens and conveyors generally used in pulp digesters andhandling equipment used in composite panel plants.

Enough material was screened and recovered during the trials to conductthe scientific work, but it was clear that more work was needed toefficiently reduce nalgrass size for commercial processes. Furtherinvestigation has shown that conventional equipment used for wood maynot produce satisfactory particle geometry for modern continuous pulpdigesters nor for many composite panel processing plants. The desiredparticle geometry is a chip of ¾ to 1 inch long by ¼ to ¾ inch wide byapproximately {fraction (3/16)} inch thick. (Note: these dimensionsapply broadly to most commercial operating mills but could vary somewhatfor certain operations.) Further, certain pulping equipment andprocesses, used principally outside the United States, can utilize awider range of particle geometry.

One representative device and method for preparing desired particlegeometry for nalgrass is shown in FIGS. 2-4. This same concept may beapplied to upgrading agricultural straws and prunings, roadside and yardclean-up, etc.

The usable stem portion of nalgrass grows from 15 to 20 feet to maturityin 12 to 18 months depending on weather and soil conditions. The stemsare harvested by cutting with a blade just above the ground line and thetop section, containing leaves and small stems, is removed by a bladecutter in the field. The resulting stems, which are essentially hollow,range from about ½ inch to 1¼ inches diameter with wall thicknessranging from just over {fraction (1/16)} inch to roughly ¼ inch. Theconcept is based on sawing the stems into “rings” of ¾ to 1 inch lengththen, “chopping” the rings into three to five pieces. Simplecalculations show that the resulting pieces would meet the optimum sizespecifications for commercial pulping and composite panel processes.

FIG. 2 is a plane view and FIG. 3 an elevation of a saw blade bed 5½feet wide with saw blades mounted on a shaft and spaced 1 inch apart.This width was selected for illustration purposes because automatic sawsused in composite panel and wood products plants range from 4 to 8 feetin width to cut panels into sections for various products. However, itwould be possible to have a much more narrow or wide saw bed dependingon economic factors of construction cost and capacity requirements. FIG.4 is a detail section of the blade and finger arrangement. Thisillustration shows a circular saw configuration however, a band sawprinciple can be employed.

Blade spacing of 1 inch is also used for illustration since spacing of ¾to 1½ inches more or less is possible depending on the desiredapplication. Nalgrass stems are pre-cut to approximately 4 to 5 feetlengths and aligned and fed into the hopper which is mounted above theapron that feeds the saw blade arrangement. Fingers mounted on a chain,belt, or other carrier mechanism are driven through a slot in the beltthat feeds into the saw blades. These fingers pull the nalgrass stemsthat feed by gravity or by a positive feed mechanism (the stems are notcompletely straight and a positive feed to clear the hopper dischargeinto the fingers can be used) from the hopper onto the apron into andthrough the saw blades resulting in rings of nalgrass discharging to achute that then flows into the chopping mechanism. The width of thefingers for a 1 inch saw blade can be ½ to ¾ inch in order to supply thepositive force to gently pull the stems through the blades.

The “chopper” may be one of several possible designs. The representativedesign shown is of a type with blades mounted on a shaft that can rotateat a single or variable speed. As rings fall into the housing around theblades, they are chopped by the action of the blade impinging on or nearthe wall. An alternate design uses hammers instead of blades or even adrum with blades and an annular space whereby chunks are pulled from thenalgrass rings. The optimal design produces the fewest small slivers orshards.

After the chopper, a screen removes the oversize (intact or nearlyintact rings) for return to the chopper and the undersize slivers andshards are removed by screening. The main stream is conveyed to aholding bin to be loaded into trucks or railcars.

Variations of this basic process are possible. The saw blades may beoscillating if a more positive cutting action is needed. The saw bladesmay have many or very few or no teeth. Another design, as noted earlier,may use a band saw principle rather than a circular one. The bands wouldhave an up and down motion as the stems are pulled through. Nonetheless,the method involving cutting rings to optimum length then reducing therings to desired particles is the same in all versions.

A key to many of the design features is the capacity of the system. Forgeneral efficiency and adequate customer service to large processingplants, a system in the field would need to produce a minimum of 10tons/hour up to 30 or more tons/hour and operate effectively 16hours/day and 6 or 7 days per week, 50 to 52 weeks per year. Tons inthis reference are short tons, 2000 lbs., and as “green” tons. In theindustry, tonnage frequently means “bone dry tons”. Based on the bulkdensity of the stems, some rough estimated calculations and sketchesshow that each if each finger “pulled” a small bundle about 10 inches indiameter, roughly 6 to 7 pounds, the fingers would need to pass theblades (about 30 inches in diameter) at a rate of just over one persecond to process 10 to 12 tons per hour. Relating that speed to similartypes of processes conceptually seems that a speed of 2 to 3 secondswould be needed to accomplish the sawing of a bundle that size. Band sawblades of 30 to 40 inch length could possibly saw bundles up to 15inches in diameter and that design could process 10 to 12 tons per hour.Larger bundles being pulled through may begin to crush the stems beforethey can be cut into the desired ring shape.

Example 2

The Formation of Representative Nalgrass Particle Boards

The protocol for manufacturing particle board of nalgrass, and ofcomparison materials, is described in this example.

Preparing the Furnish (Particles). Arundo donax stalks were chipped intopieces of approximately 2 to 3 in. long×¼ to ⅜ in. wide×0.03 in. thickin a Pallmann Drum Flaker, dried to 8% moisture, and then processed in aPrater Blue Streak hammermill with a ⅛ in. screen. Material from themill was screened resulting in 32% through the screen to be used forface material and 68% on the screen to be used for core material.

For wood (southern pine) composite preparation, commercially obtainedface and core material was used. The commercial face material wascoarser than that used for nalgrass and wheatstraw so a portion of thewood face material was screened, using the same mesh screen as used fornalgrass.

For wheatstraw, the straw was processed through the Prater Blue Streakhammermill with a ⅛ in. screen. Material from the mill was screened inthe same manner as nalgrass with 24% through the screen to be used forface material and 76% on the screen to be used for core material.

All prepared test materials were processed as follows. Each test hadthree replications at low (2%), medium (4%), and high (6%) resincontent; and low and high density. A total of 18 test panels was usedfor each material. See Table 1.

Resin/Binder addition. Core material and face material portions wereweighed out and individually put into a laboratory blender designed toduplicate production conditions. For each portion, the methyldiisocyanate resin, generally referred to as MDI, was weighed to achievethe target percentage and put into a reservoir that feeds into nozzledspray apparatus. The nozzles were positioned in the blending chamber andsprayed for 60 to 180 seconds while the blender was operating. Theblender was stopped and the resin-coated material removed. In all tests,resin content of the face and core materials was the same.

Mat Forming. Two small portions of face material and one of corematerial were weighed out for each mat to be pressed into a 3-layer testpanel. A Teflon® sheet, to ease test panel release after pressing, wasplaced on a steel sheet, and a rectangular wooden frame placed on theTeflon® sheet. The frame measured 16 in.×20 in., (the target size of thefinished test panel) and was 6 in. high. Face material was distributeduniformly inside the frame to form the lower face, then the corematerial was distributed uniformly over the face layer. Finally, theremaining portion of face material was distributed uniformly as a toplayer. The mat formed by the layers was tamped down, the frame removed,and a Teflon® release sheet placed on top of the mat.

Panel Forming. The mat was placed on the lower platen of a Siempelkamppilot model press. The platen dimensions of the press were 23 in.×31 in.and it was driven by a 200 ton servohydraulic system. A three-stagepress schedule was preset on a computer to compress to 0.75 in. in 60seconds, to remain at that thickness for an additional 400 seconds, andthen to vent for 20 seconds for a total press time of 480 seconds.Platen temperature was 330° F. At the end of the press time, the topplaten withdrew to its starting distance and the panel was removed andallowed to cool at ambient conditions.

Composite panels were manufactured from nalgrass, wheatstraw, andsouthern pine. From each panel two specimens were cut and tested instatic bending of modulus of rupture, and modulus of elasticity; fourfor internal bond strength; and one for screw withdrawal. One specimenfrom six of the 18 panels of each furnish was used to measure waterabsorption and thickness swell.

Mechanical tests were conducted on ambient-conditioned specimens using ascrew-driven universal test machine according to ASTM D1037, with a fewexceptions noted below.

Static bending specimens were roughly 2 in.×19 in.×¾ in. instead of 3in.×20 in.×¾ in. as specified for specimens with thickness greater than¼ in. The test speed was 0.36 in./min. and the span was 18 in.

Internal bond strength specimens were 2 in.×2 in.×¾ in. and tested at aspeed of 0.06 in/min. Centerline and surface breaks were recorded foreach internal bond test.

Screw withdrawal specimens were 3 in.×6 in.×¾ in. instead of 3 in.×6in.×1 in. as specified for face screw withdrawal and 2½ in.×4½ in.×¾ in.for edge screw withdrawal. The test speed was 0.06 in./min. Two edge andtwo face screw pull tests were conducted on the same specimen.

Water absorption and thickness swell were measured on 6 in.×6 in.specimens after they soaked in distilled water for 2 and 24 hours.Thickness was measured at four locations and averaged for each specimen.Water absorption and thickness swell were determined as a percentage ofthe unsoaked weight and averaged thickness for each specimen.

All mechanical and physical properties were averaged over the threespecimens for each type of panel. The mean values in the graphs in Table1 (below) represent the averages for the respective panel type.

All tests were conducted according to “Standard Methods of Evaluatingthe Properties of Wood-Base Fiber and Particle Panel Materials,” ASTMD1037. All panels were first cut into 14 inch×19 inch sections.Specimens were cut from these for testing.

Static Bending—Modulus of Rupture (MOR) and Modulus of Elasticity (MOE).Two specimens of 2 in.×19 in. were cut from each panel providing a totalof six specimens for each combination of density and resin level.Specimens were placed on a United Model No. SFM-10 screw-driven testmachine set for a span of 18 in. A computer assisted program set thetest speed at 0.36 in./min. and recorded the elasticity and rupturecurves. The six results for each combination were averaged and recordedin Table 1.

Tensile Strength Perpendicular to Surface—Internal Bond (IB). Four 2in.×2 in. specimens were cut from each test panel. Metal loading blockswere cemented to both faces of the specimen and allowed to curecompletely. The blocks were engaged on a Model SFM-10, and tested at aspeed of 0.06 in./min. Internal bond breaks were automatically recorded.Test results were averaged for the specimens for each density and resincombination, and recorded in Table 1.

Direct Screw Withdrawal; Perpendicular and Edge. One specimen of eachtest panel was prepared with two face and two edge pulls per specimen.Face withdrawal specimens were 3 in.×6 in.×¾ in. for face pulls and 2½in.×4½ in.×¾ in. for edge pulls (ASTM D1037 recommends 3 in.×6 in.×1in.). Standard pilot holes were drilled and standard screws inserted.Specimens were anchored to a platen, screw heads gripped with a loadingfixture, then withdrawn by separating the platens at the standard rateof 0.6 in./min. Force required to withdraw the screws was recorded. Testresults for specimens with the same combination of density and resinlevel were averaged, and recorded in Table 1.

Water Absorption and Thickness Swelling. One specimen of 6 in.×6 in. ofeach combination was immersed in distilled water at ambient temperaturefor 2 and 24 hours. Thickness was measured at four locations on thespecimen using a thickness gauge, and averaged. Weights at each periodwere recorded. Water absorption and thickness swell were calculated aspercent gains over the unsoaked weights, and recorded in Table 1. TABLE1 Comparative Test Results for Composites Formed from Nalgrass,Wheatstraw, Southern Pine (coarse) and Southern Pine (fine) Face EdgeResin MOE Internal Screw Screw 2 hour % 2 hour % 24 hour % 24 hour %Level Type of Specific MOR (psi × Bond Pull Pull Water Thickness WaterThickness (%) Furnish Gravity (psi) 10⁶) (psi) (lbs) (lbs) AbsorptionSwell Absorption Swell Grade 2 nalgrass 0.73 2710 0.499 123 303 243 7.23.6 37.1 13.2 M-1, S, 2, 3 2 wheatstraw 0.7 2690 0.476  46+ 166 181 7.83 42.5 13.8 None 2 s. pine- 0.71 1770+ 0.321+ 184 313 271 86 25.7 97.329.1 M-1 coarse 2 s. pine-fine 0.7 1415+ 0.272 122 275 221 80.6 21.895.7 24.5 None 2 nalgrass 0.79 3290 0.585 153 391 347 5.5 3.2 27.8 12.3M-1, S, 2, 3 2 wheatstraw 0.74 3275 0.533  59+ 205 199 6.9 2.9 39.2 12.8M-1 2 s. pine- 0.76 2170+ 0.389+ 197 375 326 52 24.7 79.6 35.2 M-1, S, 2coarse 2 s. pine-fine 0.77 1940+ 0.342 140 298 262 66.9 23.7 87.4 28.2M-1, S 4 nalgrass 0.72 3250 0.528 182 420 355 6.4 2.4 28.2 8.2 M-1, S,2, 3 4 wheatstraw 0.7 4270 0.538 103 268 253 5.9 1.8 35.4 10.8 M-1, S,2, 3 4 s. pine- 0.72 2510 0.394+ 249 342 287 38.7 12.5 76.7 20.1 M-1, S,2 coarse 4 nalgrass 0.79 3930 0.618 220 439 400 5.1 2.3 22.5 7.8 M-1, S,2, 3 4 wheatstraw 0.76 4370 0.599 119 308 278 4.7 1.7 28.5 9.6 M-1, S,2, 3 4 s. pine- 0.78 3200 0.473 305 496 389 29.2 11.3 69.9 22.9 M-1, S,2, 3 coarse 6 nalgrass 0.72 3730 0.568 237 437 361 5.5 1.9 23.5 6.2 M-1,S, 2, 3 6 wheatstraw 0.69 4500 0.582 126 286 283 5.1 1.6 30.1 8.8 M-1,S, 2, 3 6 s. pine- 0.7 2430 0.369+ 324 441 480 26.2 5.2 79.9 15.1 M-1,S, 2 coarse 6 nalgrass 0.78 4460 0.645 292 522 486 4.6 1.8 18.6 5.6 M-1,S, 2, 3 6 wheatstraw 0.76 5190 0.662 153 346 308 4.5 1.4 25.7 8.5 M-1,S, 2, 3 6 s. pine- 0.78 3380 0.51 343 488 452 13.2 2.7 51.6 15.9 M-1, S,2, 3 coarse+Denotes the properties that limit grade acceptance.MOE and MOR are averages of two specimens with three replications.Internal bond is average of four specimens with three replications.Water absorption is one specimen with one replication.Screw pulls are averages of two specimens with three replications.

The results show that at a 2 weight percent resin level and low densitytrial, the nalgrass composite exceeds the maximum for the highestindustry grade standard for medium density particleboard (ANSI; M-3)whereas neither the wood composite nor the wheatstraw composite meetseven the minimum grade standard (ANSI; M-1). See Tables 1 and 2. The 2weight percent nalgrass composite shows significantly less waterabsorption and thickness swell than the wood-based composites. Moreover,the internal bond strength of nalgrass is significantly higher than thatof the wheatstraw composite which fails to meet minimum standards. Thesesuperior physical properties are also apparent at the 4 and 6 weightpercent resin levels.

With regard to the screw pull test, the nalgrass composites perform atleast as well as the wood-based composites, and exceeds significantlythe performance of wheatstraw composites. The modulus of elasticity(MOE) of nalgrass exceeds that of wheatstraw and wood-based composites,for almost every level of resin addition, except at the 6 weight percentlevel. At this level of resin addition, wheatstraw composite appears tohave a slightly higher modulus of elasticity.

With regard to modulus of rupture (MOR), nalgrass composite againexhibits superior performance as compared to wood-based composite. Thewood composite fails to make the minimum (M-1) industry grade standard.When compared to wheatstraw composite, nalgrass composite is superiorwhen the resin level is low, such as 2 weight percent. As the resinlevel increases, wheatstraw composite MOR exceeds that of the nalgrasscomposites. This demonstrates one of the advantages of nalgrasscomposite, namely, that good physical properties are achievable at lowresin levels.

Example 3

The Formation of Representative Nalgrass/Southern Pine Particleboards

In this example, the formation of particle boards containingnalgrass/southern pine blends is described. The mechanical and physicalproperties of the particle boards compared to particle boards formedfrom (1) nalgrass and (2) southern pine.

Tests were conducted to compare the mechanical and physical propertiesof nalgrass, southern pine, and nalgrass/southern pine particleboard.For each furnish type, panels were manufactured with target densities of42 lb/ft³ and 47 lb/ft³ and resin levels of 2% and 4%. All specimenswere tested in static bending, internal bond strength, face and edgescrewholding, water sorption, and thickness swell. Mechanical propertieswere compared with product specifications for medium densityparticleboard (ANSI A208.1-1993). See Table 2. TABLE 2 GradeSpecifications of Medium Density Particleboard (National ParticleboardAssociation ANSI A208.1-1993) MOR MOE IB FSP ESP Grade (psi) (ksi) (psi)(lb) (lb) M-1 1595 250 58 NS NS M-S 1813 276 58 202 180 M-2 2103 326 65225 202 M-3 2393 399 80 247 225

An electrically heated, computer automated hot-press was used tomanufacture all panels. The press was equipped with nominal 23×31 inchplatens, which were driven by a 200 ton servo-hydraulic system. Thepress was controlled using platen position with a three-stage pressschedule that included: (1) press closing for 60 seconds; (2) panelpressing for 400 seconds; and (3) venting for 20 seconds. The platentemperature was 330° F. All panels were formed to dimensions of 16×20×¾inch, but trimmed to 14×19×¾ inch.

Panels were manufactured from nalgrass, southern pine, andnalgrass/southern pine at target densities of 42 lb/ft³ and 47 lb/ft³and diphenylmethane diisocyanate (MDI) resin levels of 2% and 4%. Twelvepanels of each furnish were manufactured at the different combinationsof density and resin loading (i.e., three panel replicates percombination). From each panel two specimens were cut and tested instatic bending for modulus of rupture and elasticity, four for internalbond strength, and one for water sorption/thickness swell. One specimenfrom four of the twelve panels of each furnish was used to measure faceand edge screw holding capacity. Each specimen had a different densityand resin level.

Mechanical tests were conducted on ambient-conditioned specimens using ascrew driven universal test machine in general accordance to ASTM D1037. Static bending specimens were nominally 2×19×¾ inch (ASTMspecifies dimensions of 3×20×¾ inch for specimens with thickness greaterthan ¼ inch). The test speed was 0.36 in/min and the span was 18 inches.Internal bond strength specimens were 2×2×¾ inch and the test speed was0.06 in/min. Screwholding specimens were 3×6×¾ inch for facescrewholding (ASTM specifies dimensions of 3×6×1 inch) and 2½×4½×¾ foredge screwholding. The test speed was 0.06 in/min. The two edge and twoface screwholding tests were conducted on the same specimen. Watersorption and thickness swell were measured on 6×6 inch specimens afterthey soaked in distilled water for 24 hours. Thickness was measured atfive locations, and averaged for each specimen.

A three-way analysis of variance (ANOVA) was performed on all mechanicaland physical properties using density, resin level, and furnish as thethree factors.

In general, for each density and resin level combination, the modulus ofrupture (MOR) and modulus of elasticity (MOE) significantly increased asthe proportion of nalgrass particles within them increased (Table 3). Incontrast, the internal bond strength (IB) of panels consistingpredominantly of nalgrass particles were significantly lower thansimilar panels made predominantly of southern pine particles. For face(FSP) and edge (ESP) screwholding, there were few significantdifferences between any of the panels. For the most part, all panelsexceeded the highest grade specifications as stipulated by ANSIA208.1-1993 (Table 2). TABLE 3 Average Mechanical Properties of VariousNalgrass, Southern Pine and Nalgrass/Southern Pine ParticleboardsFurnish Nalgrass: Resin Highest Southern Target Density Loading MOR MOEIB FSP ESP Grade pine (lb/ft³) (psi) (psi) (ksi) (psi) (lb) (lb)Acceptance 100:0  42 2 2709 (183) 500 (19) 123 (17) 303 (48) 243 (29)M-3 80:20 42 2 2467 (194) 493 (33) 148 (22) 303 (160) 253 (6) M-3 60:4042 2 2343 (229) 464 (280) 158 (17) 317 (18) 314 (97) M-2 40:60 42 2 2210(152) 416 (230) 147 (16) 327 (1) 274 (32) M-3 20:80 42 2 2362 (283) 429(262) 167 (14) 314 (12) 278 (21) M-3  0:100 42 2 1769 (119) 321 (10) 184(18) 313 (46) 271 (33) M-S 100:0  42 4 3252 (238) 529 (17) 182 (14) 420(65) 355 (36) M-3 80:20 42 4 3414 (2440) 527 (19) 201 (34) 357 (5) 301(30) M-3 60:40 42 4 3263 (258) 521 (24) 223 (20) 386 (61) 375 (19) M-340:60 42 4 3176 (228) 526 (18) 230 (35) 384 (8) 341 (60) M-3 20:80 42 42807 (577) 458 (63) 238 (28) 443 (6) 357 (18) M-3  0:100 42 4 2272 (410)363 (54) 249 (50) 343 (50) 288 (53) M-2 100:0  47 2 3297 (286) 586 (22)153 (19) 391 (37) 347 (22) M-3 80:20 47 2 3069 (327) 583 (17) 173 (20)338 (18) 341 (6) M-3 60:40 47 2 3111 (309) 581 (8) 170 (34) 409 (16) 369(20) M-3 40:60 47 2 2736 (185) 499 (12) 163 (41) 380 (16) 324 (1) M-320:80 47 2 2993 (204) 516 (23) 199 (30) 439 (14) 404 (18) M-3  0:100 472 2230 (180) 390 (26) 197 (31) 392 (44) 327 (52) M-2 100:0  47 4 3297(265) 618 (15) 220 (19) 439 (64) 401 (40) M-3 80:20 47 4 4301 (487) 666(570) 253 (26) 442 (8) 410 (40) M-3 60:40 47 4 3852 (298) 597 (24) 275(22) 512 (64) 461 (2) M-3 40:60 47 4 3883 (452) 632 (24) 273 (34) 517(18) 499 (15) M-3 20:80 47 4 3933 (219) 580 (15) 272 (28) 498 (4) 429(40) M-3  0:100 47 4 3202 (289) 473 (22) 305 (27) 496 (38) 390 (42) M-3

For all furnishes, mechanical properties generally increased as densitylevel increased from 42 lb/ft³ to 47 lb/ft³ and as resin level increasedfrom 2% to 4%.

The three-way ANOVA indicated that resin level, density, and furnishstatistically influenced all mechanical properties. The effect of paneldensity in relation to material IB strength was dependent on resinloading, while the effect of resin loading in relation to material MOEwas dependent on furnish type.

After soaking in distilled water for 24 hours the water sorption andthickness swell of the panels containing a higher proportion of nalgrassparticles were in general lower than panels incorporating a higherproportion of southern pine particles (Table 4). TABLE 4 AveragePhysical Properties of Various Nalgrass, Southern Pine andNalgrass/Southern Pine Particleboard Furnish Nalgrass: Target ResinSouthern Density Loading WA 24 Hour TS 24 Hour Pine (lb/ft³) (psi) (%)(%) 100:0  42 2 37.1 13.3 80:20 42 2 61.5 (5.4) 23.6 (0.9) 60:40 42 279.7 (2.9) 27.3 (0.3) 40:60 42 2 89.7 (1.0) 28.8 (1.6) 20:80 42 2 79.3(5.4) 29.7 (0.6)  0:100 42 2 97.3 29.2 100:0  42 4 28.2 8.2 80:20 42 427.8 (1.6) 10.2 (0.6) 60:40 42 4 50.2 (3.5) 16.4 (0.2) 40:60 42 4 63.3(7.8) 18.3 (0.4) 20:80 42 4 69.8 (4.9) 19.6 (0.5)  0:100 42 4 76.7 20.1100:0  47 2 27.9 12.3 80:20 47 2 39.0 (2.3) 18.7 (1.6) 60:40 47 2 64.0(7.9) 27.2 (2.2) 40:60 47 2 80.7 (1.5) 32.4 (2.3) 20:80 47 2 79.3 (5.4)30.5 (0.2)  0:100 47 2 79.6 35.3 100:0  47 4 22.6 7.8 80:20 47 4 19.3(0.8) 8.7 (0.1) 60:40 47 4 32.5 (5.0) 12.4 (1.3) 40:60 47 4 50.4 (14.1)17.9 (2.1) 20:80 47 4 63.7 (4.6) 21.2 (0.1)  0:100 47 4 70.0 23.0

Values in parentheses indicate associated standard deviations.

Water sorption and thickness swell after 24 hours generally decreased asdensity level increased from 42 lb/ft³ to 47 lb/ft³ and as resin levelincreased from 2% to 4%. The three-way ANOVA indicated that the effectof panel density in relation to thickness swell was dependent on furnishtype, while the effect of resin loading in relation to both thicknessswell and water sorption was dependent on furnish type.

Generally, the use of nalgrass particles would be best to obtain panelsof superior strength and stiffness. The addition of southern pineparticles to a furnish, by an amount as low as 20%, although slightlyaffecting panel strength and stiffness, significantly increases internalbond strength.

As panel density and resin loading increased mechanical propertiesincreased. In a commercial market, however, panels of the lower densityand lower resin loading would be economically preferable while stillattaining wide grade acceptance.

Panels made predominantly from nalgrass particles exhibited preferablewater sorption and thickness swell characteristics to panels madepredominantly from southern pine particles. Water sorption and thicknessswell, after 24 hours water submersion, were generally reduced by anincrease in panel density and resin loading.

Example 4

Utilization of Arundo Donax in Paper Production: Kraft and AlkalinePeroxide Mechanical Pulping

In this example, the utilization of Arundo donax (nalgrass) in theproduction of paper is described. The pulping behavior and pulpproperties of nalgrass is also described. Data from kraft pulping, sodapulping, and alkaline peroxide mechanical pulping of nalgrass ispresented.

The tests were to be performed on laboratory and small pilot plantscale. The Pulp and Paper Science Department of the University ofWashington was selected for kraft and soda pulping tests and theDepartment of Wood and Paper Science at North Carolina State Universityfor the alkaline peroxide mechanical pulping tests. All testing ofhandsheet paper samples was made by the Pulp and Paper ScienceDepartment of the University of Washington.

Kraft pulping was found to proceed rapidly and resulted in relativelyhigh yields of easily bleached pulp. Average fiber length was highcompared to other nonwood materials and, in fact, slightly higher thanthat from aspen hardwood. Strength properties were better than aspenhardwood kraft in tear and tensile.

Raw Material. Material for the present study was cut fresh from growthsin Orange County, Calif. and shipped without drying to the University ofWashington.

The nalgrass stem has a dense ring of tissue surrounding a hollow core.Stem diameters are typically ¾ to 1¾ inches in diameter. It can be cutor milled into lengths similar to wood chips and once crushed to breakthe circular cross section has bulk density similar to that of woodchips (Table 5). TABLE 5 Bulk Density Nalgrass Wheatstraw N.W. SoftwoodUncompacted, green BD lb/ft3 10.8 2-6 12-14 Compacted, green BD lb/ft312.5 3-7 12-15

In earlier tests, nalgrass chips were used. Material for the presenttrials was cut into precise lengths using a band saw then crushed. Forthe kraft pulping trials tests were made at four different cut lengths,{fraction (1/2, 3/4, 7/8)} and 1¼ inches.

The character of chipped material is important to processing intoconventional pulping equipment. The bulk density of the chipped materialis important in terms of packing into digesters and sizing of conveyorsand other process equipment. The high bulk density of chipped nalgrasswill allow it to be processed in conventional, existing chip handlingand pulping equipment. Cooking liquor to raw material ratios can be low,similar to those used for wood chips resulting in high waste liquorconcentrations.

The other important chip characteristics is the ability of the cookingchemicals to penetrate into the center of the chip during pulping.Earlier tests were done with hammermill prepared chips and were screenedto remove fines and oversized material. It was noted that there weresome long pieces (2 inch) that might hinder material flow if they werenot removed early in the processing sequence. The material gave pulpwith low uncooked rejects, indicating that the penetration of cookingliquor was quite uniform.

A sample of dried material was also included. This was cut to ⅞ inchlength and was included to evaluate whether liquor penetration washindered by drying as is the case with wood chips.

Kraft Pulping and Beaching

Kraft Pulping. Kraft cooking of the nalgrass material was made at theUniversity of Washington using a pilot digester system. Cooks were madewith each of the chip samples under conditions aimed at producingdelignification to the 20 kappa level suitable for bleaching. Pulpingconditions are given in Table 6. TABLE 6 Pulping Conditions for ChipsSize and Type Evaluation Chip Size (inch) ½ ¾ ⅞ 1¼ Veneer Cut DryH-Factor 850 850 850 850 850 850 Temp (C.) 170 170 170 170 170 170Liquor/Reed 4.5 4.5 4.5 4.5 4.5 4.5 EA (%) 15 15 15 15 15 15 Sulfidity(%) 24.4 24.4 24.4 24.4 24.4 24.4 Kappa No 17.4 14.0 17.6 18.2 14.6 14.9Rejects (%) 1.1 0.9 3.6 3.2 0.2 3.3

All samples cooked with similar results. The cooking time is short asindicated by the low H Factor (a chemical reaction value combiningtemperature and reaction time). Cooking times would be up to half thoseof softwoods. The high bulk density of the nalgrass chips also alloweduse of a low liquid to chip ratio similar to that used for wood chips.This indicates that nalgrass pulping could be made in the same equipmentas wood chips and with the same heat economy. Typical low density strawand other nonwood plant material require high liquor to wood ratiosalthough cooking is rapid as found with this nalgrass material.

The four various lengths of chips show only small, probablyinsignificant, differences in pulping response. Although the ¾ inch chiphad slightly lower kappa, 14.0 vs. 17.6-18.2 for the longer chips, the ½inch chip gave 17.4 kappa. The uncooked rejects were lower in the shortcut chips, 0.9-1.1%, compared to the longer chips, 3.2-3.6%, but theselevels are low, indicating that uniform penetration of cooking liquorsinto the material occurred and also showing that the nodes cooked well.The nodes of grasses, of which nalgrass is a member, are sometimesresistant to pulping.

The veneer cut chips cooked similarly to the saw cut chips, giving lowkappa, 14.6, and low rejects, 0.2%. This type of chip preparation wouldbe satisfactory for commercial operations.

The dried material showed pulping response similar to the freshmaterial, kappa 14.9, rejects 3.3%, indicating that there are noproblems with the penetration of liquor into dry nalgrass chips. Thismeans that chips could be used from fresh or dry material withoutsignificant changes in process conditions.

The pulping of the ⅞ inch cut nalgrass is compared to typical hardwoodand softwood kraft pulping in Table 7. The nalgrass cooks more rapidlythan both types of wood, requires less chemical and produces onlyslightly higher rejects (a not significant difference). TABLE 7 PulpingConditions for ⅞ Inch Chip Size Compared to Wood Chips Hardwood SoftwoodMaterial ⅞ inch Nalgrass Typical Typical H-Factor 850 1200 1800 Temp(C.) 170 170 170 Liquor/Material 4.5 4.5 4.0-4.5 EA (%) 15 17 18Sulfidity (%) 24.4 25.0 25.0 Kappa No 17.6 25 28 Rejects (%) 3.6 3.0 1.5

Bleaching. Most published work on the bleaching of nonwood material ismade using the now outdated Chlorine (C), Extraction (E), Hypochlorite(H) bleach sequence. Worldwide this sequence is typically used but it isnot now acceptable environmentally in the U.S. to meet presentenvironmental standards bleaching of kraft pulp has to be with anElemental Chlorine Free (ECF) method. Bleaching tests were made on pulpfrom a larger scale cook on the ⅞ inch cut material using an ECF bleachconsisting of Chlorine dioxide (Do). Extraction with oxygen and peroxide(Eop). Chlorine dioxide (D1). The results are shown in Table 8. TABLE 8Bleach Response Stage Do Eop D1 D.Eop.D. Bleach Sequence-0.20 KappaFactor Consistency (%) 10 10 10 Kappa Factor 0.2 — — Time (min) 30 90120 Temp (C.) 60 100 70 O2 (psi) — 30 — H2O2 (%) — 0.7 — NaOH (%) — 1.7— ClO2 (%) 1.34 — 1.5 pH 3.3 9.5 3.4 Brightness (% ISO) — — 83.84 D1 D1Stage Do Eop (run 1) (run 2) D.Eop.D Bleach Sequence-0.25 Kappa FactorConsistency (%) 10 10 10 10 Kappa Factor 0.2 — — Time (min) 30 90 120120 Temp (C.) 60 100 70 70 O2 (psi) — 30 — H2O2 (%) — 0.7 — NaOH (%) —1.7 — ClO₂ (%) 1.68 — 1.25 1.5 pH 3.3 9.5 3.4 Brightness (% ISO) — —85.6 86.4

Initially, a chlorine dioxide charge in the first stage of 0.20 kappafactor (percentage equivalent chlorine/kappa number) was applied,followed by 1.5% chlorine dioxide in the third stage. This resulted in abrightness of 83.8%. Modification to a 0.25 kappa factor application inthe first stage resulted in brightness of 85.6 and 86.4 with 1.25% and1.5% chlorine dioxide in the third stage, respectively.

A total chlorine dioxide charge of 3.18% was required for the 86.4. Inearlier tests, a brightness of 90.0 was reached in a five stage bleachusing 4.34% chlorine dioxide. Softwood kraft pulps typically require 5.8to 6.2% chlorine dioxide to reach a brightness level of 90.0%.

Handsheet Properties. Standard testing of pulp properties was made usingTAPPI procedures. Pulp from the ⅞ inch chip sample was beaten in a PFImill to various freeness levels. The PFI mill is a standard laboratorypulp beating apparatus used to simulate refining in commercialpapermaking operations. Typically the initial pulp freeness of 600 to750 ml CSF is reduced to about 400 to 500 ml before papermaking todevelop strength properties, tensile strength is increased with somesmall loss of tear strength.

Handsheets were made from ⅞ inch of cut nalgrass pulp beaten to severalfreeness levels and tested for strength properties, (Table 9). Pulpsfrom the other chip cut lengths were beaten to the 400 ml CSF level forcomparison. TABLE 9 Handsheet Strength Tests Chip Size Freeness Tensile(inch) PFI (K) (ml) Burst Index Tear Index Index seven-eighth 0 700 2.513.99 41.55 1 605 3.80 10.39 63.50 2 488 4.75 9.38 72.42 3 415 5.10 9.1578.93 3.2 404 4.48 9.38 75.10 3.6 391 5.01 9.40 78.29 half-inch 0 7332.56 4.69 39.36 3.2 413 4.78 8.78 77.60 three-fourth 0 700 3.11 3.9949.82 3.2 393 5.08 9.30 79.98 one and 0 709 3.07 4.24 47.22 one-fourth3.2 393 5.25 9.04 81.21

The initial pulp freeness before beating was 700 ml CSF which is a veryhigh and desirable level compared with typical nonwood material. Inearlier tests a similar high initial freeness of 630 ml CSF was found.These compare to >700 ml for softwood pulps and 600-650 for hardwoodpulps and are favorably high, allowing the papermaker to modify the pulpproperties without restriction and to allow high drainage in thepapermaking operation.

The handsheet strength measurement, burst, tensile and tear, are all atfavorable levels and higher than those obtained in earlier tests.Comparison of the two sets of results from nalgrass and from typicalwheatstraw, kenaf, hardwood and softwood are shown in Table 10. Thenalgrass has remarkably high strength in all categories. The sheet bulkis high compared to other nonwoods which indicates the material hassignificantly different characteristics than the straws. TABLE 10Comparison of Nalgrass with Other Pulps Whole Aspen Nalgrass A NalgrassB Wheatstraw Kenaf Kraft D Fir Kraft Freeness, ml 400 400 400 400 400400 PFI Mill, revs. 3200 900 400 — 464 8100 Burst Index 4.5 — — 5.5 2.16.8 Tear Index 9.4 8.7 3.7 10 7.6 22.4 Tensile Index 75 53 40 65 46 92Bulk, cc/g — 1.59 1.24 — 1.43 1.81 Brightness, % 86 90 85 — 89 89

Example 5

Caustic Peroxide Cooking of Arundo Donax

In this example, the caustic peroxide cooking of Arundo donax (nalgrass)is described. Flakes of Arundo Donax obtained from Orange County, Calif.were evaluated under a variety of cooking conditions using alkali (e.g.,potassium hydroxide and/or sodium hydroxide) in combination withhydrogen peroxide. A series of experiments were conducted varyingcooking time and temperature.

In one method, sodium hydroxide (10 percent by weight based on oven drychip basis) and hydrogen peroxide (5 percent by weight based on oven drychip basis) were used and the chips cooked for 90 minutes at 90° C. Thechips were dramatically softened and then broken down by mechanicalaction. A Morden hydropulper and Sprout lab refiner were used to processthe chips. The yields from the method were in the range from about 65 toabout 70 percent. The resulting pulp had a brightness in the range fromabout 45 to about 50 (unbleached). The tensile index was greater thanabout 50 Nm/g for all conditions.

The alkali and peroxide at high temperature results in the breakdown ofthe waxy portion of the Arundo Donax particles. The waxy material hasbeen determined to be detrimental in traditional chemithermomechanicalpulping (CTMP) processes for fiber-to-fiber bonding.

Arundo Donax can be processed utilizing existing secondary fiber pulpingtechnology by, for example, mills that repulp old newsprint (ONP) or oldmagazines (OMG). These processing methods include a hydropulper usingalkaline chemistry with hydrogen peroxide. In the method, Arundo Donaxchips or flakes are allowed to sit in a hydropulper for a period of timeunder the prescribed conditions, then either (1) while from the firstchemical treatment, or (2) at the end of the cooking period, the chipsor flakes are broken down by the mechanical action of the hydropulper.The pulp/cooked chips or flakes can then be pumped to an additionalmechanical stage such as, for example, a refiner or a kneader. The pulpthen sees further mechanical action as it is being pumped back to thehydropulper. The result is an enhancement of the overall yield in theprocess.

While the preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.

1-43. (canceled)
 44. A method for forming an Arundo donax paper product,comprising: (a) subjecting a furnish comprising Arundo donax particlesto a pulping process comprising cooking the furnish using an H-factor ofabout 850; (b) depositing the furnish onto a foraminous support; (c)dewatering the deposited furnish to provide a fibrous web; and (d)drying the web to provide a paper product.
 45. The method of claim 44,wherein the Arundo donax furnish further comprises wood fibers. 46-59.(canceled)
 60. A method for making a paper product, comprising: (a)depositing a furnish comprising Arundo donax pulp onto a foraminoussupport; (b) dewatering the deposited furnish to provide a fibrous web;and (c) drying the web to provide a paper product.